RewriteEngine On
RewriteCond %{THE_REQUEST} " /pages/page_0\.aspx\?id_page=272&id_region=1 "
RewriteRule ^ https://newsite.ru/b.html? [L,R=301]
RewriteCond %{THE_REQUEST} " /pages/page_0\.aspx\?id_page=888&id_region=34 "
RewriteRule ^ https://newsite.ru/ccc.html? [L,R=301]
RewriteRule ^ https://newsite.ru/ [L,R=301]
Или
RewriteEngine On
RewriteCond %{QUERY_STRING} (^|&)id_page=272($|&)
RewriteCond %{QUERY_STRING} (^|&)id_region=1($|&)
RewriteRule ^pages/page_0\.aspx$ https://newsite.ru/b.html? [L,R=301]
RewriteCond %{QUERY_STRING} (^|&)id_page=888($|&)
RewriteCond %{QUERY_STRING} (^|&)id_region=34($|&)
RewriteRule ^pages/page_0\.aspx$ https://newsite.ru/ccc.html? [L,R=301]
RewriteRule ^ https://newsite.ru/ [L,R=301]